This invention relates in general to means for associating one part relative to another and in particular to a new and useful method and apparatus for reproducibly adjusting the position of two mechanical parts relative to each other.
The present invention relates to a means for exactly and reproducibly adjusting the position of two mechanical parts, extending one within another, relative to each other. For example, if a shaft rotatable relative to a stationary component part is to be exchanged and, with regard to a unit connected to the shaft, the shaft head may have to be put in a definite position depending on certain reproducible limiting conditions. More specifically, in the field of so-called industrial robots or manipulators which perform certain reproducible movements through a program-controlled, electrically driven linkage, if the systems measuring the position and displacement of the individual axes of motion are to be exchanged, the axes must be brought into their so-termed mechanical zero position, whereupon the measuring system is brough into its so-termed electrical zero position. The intended result is that in any other position, the mechanism is consistent with the corresponding position of the measuring system and that there is no need for correcting the respective program control.
Another specific application connected to the employment of industrial robots is the exchange of one manipulator for another which is to be controlled by the same program. In such an instance, it is necessary to bring the mechanical and electrical zero positions of both units into agreement or at least into a definite relation to each other. To this end, the mechanical zero position of all axes must be fixed by means of a special gauge or measuring device during the first assembly, and, in addition, the manufacturing tolerances of the mechanism must not exceed certain limits. Deviations from the initial program which is stored by means of a punched or magnetic tape and may be recorded for the substitute manipulator, must not exceed a degree admissible in the specific case, considered through the entire field of operation.
A conventional method of reproducibly adjusting, for example, a rotary shaft relative to a housing in which the shaft is supported, is to provide each of the component parts with a locating bore and to bring the bores into alignment. By introducing a fitting pin, the alignment is checked and fixed. Another known method is to bring two opposite notches or scratches into alignment. As a rule, the accuracy required in the work with industrial robots cannot be achieved with these prior art methods. This is due to the always necessary tolerances on fit and to the difficulty in aligning scratches or notches with a satisfactory accuracy.